Plate for use in lining burglar-proof vaults and similar purposes



F. J. NAPOLITAN. PLATE FOR USE IN LINING BURGLAR PROOF VAULTS AND SIMILAR PURPOSES.

APPLICATON FILED AUG. 13, 1921.

Patented July 11, 1922.

UNITED STA'IJES PATENT OFFICE.

FRANCIS J'. NAPOLITAN, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO AMERICAN ABRASIVE METALS COMPANY, A CORPORATION OF NEW YORK.

PLATE FOR USE IN LINING BUEGLAR-PROOF VAULTS AND SIMILAR PURPOSES.

Application filed August 13, 1921.

T 0 all 'whom it may camera:

Be it known that I, F RANCIS J. NAPOLITAN, a citizen of the United States of America, residing at Jersey City, county of Hudson, State of New Jersey, with a post-ofiice address at 51 Tonnele Ave., Jersey City, New Jersey, have invented certain new and useful Improvements in Plates for Use in Lining Burglar-Proof Vaults and Similar Purposes, of which the following is a specification.

My invention relates to the production of plates which shall have the highest attainable resistance to the action of an oxy-acetylene burner or similar cutting torch, and at the same time be resistant to cutting tools. Plates of this character are particularly useful in lining bank vaults and safes liable to be attacked by burglars using drills and oXyacetylene torches in the efiort to penetrate to the interier of the structure, but can be employed to advantage in other situations.

I have discovered that purified and fused aluminum oxide. which is almost equal in hardness to the diamond, is the most effective material available for the formation of plates resistant to the action of drills and other cutting tools. Aluminum oxide as heretofore generally used in the arts has been quite impure. A crystalline mass of the material generally known as aluminum oxide is, in reality, an aggregate of aluminum oxide ciystals embedded in a matrix of readily fusible and structurally Weak impurities, chiefly iron oxide and silica. I have discovered, on investigation, that by chemical and other means, much of the impurities may be removed, and upon subscquent fusing in the electric furnace or other source of great heat, etc., there is produced a much purer aggregate of aluminum oxide crystals without any matrix of diluents. This melts at a temperature of approximately 2050 degrees centigrade, and consequently it is also highly resistant to the action of the oxy-acetylene torch or similar apparatus cutting by the action of heat. The crystals are in rhombohedral form, thus giving it a fairly low possibility of cleavage and considerable structural strength. This fused aluminum oxide is not workable to a degree which would render it possible to make regularly forned plates out of it, and to produce such plates it is necessary to embed in a matrix of cast iron or other metallic material the irregular masses of the fused aluminum Specification of Letters Patent.

Patented July 1 1, 1922.

Serial No. 492,202.

oxide obtained by breaking up the product of the electric furnace.

In the accompanying drawing I have shown in cross section a plate made in accordance with this embodiment of my invention.

l represents the matrix of cast metallic material, and 2, 2 represent masses of fused aluminum oxide cast and embedded therein in the form of graded aggregate, the smaller particules filling the voids between the larger ones sufficiently to make it impossible for a torch fiame or drill to pass through the plate without striking one or more of these bodies of fused aluminum oxide.

The aluminum oxide is fused, and 'perhaps re-fused, in an electric furnace so as properly to crystallize it and free it from impurities, and then broken up into smaller masses by hammering or other suitable treatment.

iVhile the fused aluminum oxide masses prepared and employed as above described have the highest possible resistance to cutting tools, they do not present an equally great resistance to an oXy-acetylene cutting torch or similar heat generating apparatus as the fusion point of the aluminum oxide is only about 2050 degrees centigrade.

I have found that the Capacity for resisting heat can be mubh increased by using an artificial spinelle in place of the fused aluminum oxide without, at the same time, materially reducing the hardness. This spinelle is a fused Inixture of aluminum oxide and magnesium oxide. On fusing these together and allowing them to crystallize they form an eutectic mixture or solid solution with aluminum oxide in excess, if the purpose is to retain in the compound the high drill resisting property of that Component to as great a degree as possible. The excess of aluminum oxide is rejected by the eutectic which forms as' a molten mass of the mixture cools, and such excess exists in the solidified state as crystals of more or less pure aluminum oxide between crystals of the spinelle. The magnesium oxide is highly refractory, fusing at about 2800 degrees centigrade, and having other qualities which make it largely immune to the disintegrating action of an oxy-acetylene cutting torch. These qualities are largely impressed on the eutectic mixture. The matrix of pure aluminum oxide retains its hardness and consequent quality for use in forming bank Vaults and similar purposes which plate comprises a matrix of cast iron or other metallic material in which are embedded closely packed masses each comprising fused and crystallized aluminum oxide in the form of a graded aggregate.

As an article of manufacture a plate for use in forming bank vaults and similar purposes, which plate comprses a matrix of cast metallic material in which are embedded closely packed masses each consisting of a fused and crystallized mixture of magnesium oxide and aluminum oxide with aluminum oxide in eXcess of that proportion required to form as eutectic wth the magiesium oxide.

FRANCIS J. NAPOLITAN.

Witness H. E. MCGUIRE. 

